It may seem like a silly question, since water is probably one of the safest things you can drink, and drowning isn’t technically an overdose. It’s certainly not the sort of frippery that you’d expect to kick off Mind the Science Gap’s winter 2013 season (Welcome back!). After all, it’s water. Well, as any toxicologist worth his (or her!) salt will tell you, it’s the dose that makes the poison, and yes, you can overdose from drinking water. In fact, there’s a fair amount of medical literature out there on the subject because it’s not as uncommon as you might think.

Although uncommon, it is possible to drink too much water. When your kidneys are unable to excrete the excess water, the electrolyte (mineral) content of the blood is diluted, resulting in low sodium levels in the blood, a condition called hyponatremia. Endurance athletes, such as marathon runners, who drink large amounts of water, are at higher risk of hyponatremia. In general, though, drinking too much water is rare in healthy adults who eat an average American diet.